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Old 29th April 2010, 12:06 PM   #31
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by currentflow View Post

you may now be tempted to try the BD829/830 in your DX Blame ES to see if the effect is as marked as Sakis found in his P3A
Im ready

But from what I have heard/read about Dx, and now here the close looking P3a, we may need the opposite of what Sakis has achieved with P3a
Dont know if that makes sense

Sakis, I hope you dont mind me showing my layout version of Dx, just to show where I would like to take it
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Old 29th April 2010, 12:34 PM   #32
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Default Sakis......nice thread

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Old 29th April 2010, 12:35 PM   #33
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to be honest with you ...no i dont mind at all but i also dont understand what oposite means ...

also i cannot understand much of your pcb or your "version" of DX

also to put things in a proper track i have no expirence with your schematic or P3A versions that drive multiple outs in such a low rail voltage ....

probably what you present is moded circuit of something else ...

kind regards sakis


( tinitus .... i can also sent you a proper pcb software for free if you want i have sprint layout 4 that i dont use any more since i have version 5 i will be more than happy to mail you a cd fo free ...probably it can make your pcb more undersatndable )
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Last edited by east electronics; 29th April 2010 at 12:38 PM.
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Old 29th April 2010, 12:49 PM   #34
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Default I will try these transistors... Sakis is mailing some to me..also i will search for

them in São Paulo....yes.... i will do it current flow...he said sound i better...i want listen that as i have tested several and no one sounded better in the VAS position... no MJE340/350, nor 2SC4793 and no MJE150128 and also tried MJE15032... some others was tried too... he perceived advantage..so.. i am interested to know that too.... he does things building and listening...so..real world effect is what i want.

Sakis is Dx Corporation of Greece...old friend that has built some nice amplifiers.... skilled...use to fix amplifier and to build amplifier for customers, Bars and Restaurants.

He is the one can answer questions and can decide things about Dx Corporation in Greece... an authorized dealer.

regards,

Carlos
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Last edited by destroyer X; 29th April 2010 at 12:54 PM.
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Old 29th April 2010, 01:24 PM   #35
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Quote:
Originally Posted by tinitus View Post
Im ready

But from what I have heard/read about Dx, and now here the close looking P3a, we may need the opposite of what Sakis has achieved with P3a
Dont know if that makes sense
Not quite!

Quote:
Originally Posted by destroyer X View Post
I will try these transistors... Sakis is mailing some to me..also i will search for them in São Paulo....yes.... i will do it current flow...he said sound i better...i want listen that as i have tested several and no one sounded better in the VAS position...
I look forward to your findings.

Regards,
Steve
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Old 29th April 2010, 03:05 PM   #36
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Default P3A is a different amplifier...alike has bootstrap...but differential current is

different (higher)...the VAS current is different (lower)..the output sounds different because it is another type... the decision about input input capacitor is very different... the decision taken about the Miller is also different..another philosophy, another idea, that has its own advantages and disadvantages.... worries about waveform and distortion above the human audibility limits is also different..seems he does not worry about things we cannot listen..he is rigth once again.

It sounds good...i have built it several years ago and now i have measured in the simulator.

Performance measured is different when compared to the Dx Amplifier, as an example ....another bootstrapped amplifier....listening it is also very different....but in the scope if performs even better than the Dx amplifier...simulator is a little bit worse..but difference is below human capacities to detect.... say, one amplifier having 0.023% THD and other having 0.048% THD.

So, Rodd, as usual, is rigth.... very simple and having very good performance..not to be underestimated.

Our masters, our teachers, these men... Rodd, Hugh, Nelson Pass, Douglas Self, Slone, Duncan, JLH and others are the ones we should respect and try their designs.

In my simulator schematic, the CCS control of current, the resistance, was reduced to obtain 300uV off set instead of 41 milivolts (not bad too..this means nothing...small power)...the bias resistance, the one should be adjusted, a variable 2K trimpot...was adjusted to obtain 100mA each rail... interesting..the amplifier does not accept tweaks in the Miller capacitor..the value should be the one Rodd has pointed us.

regards,

Carlos
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Last edited by destroyer X; 29th April 2010 at 03:14 PM.
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Old 29th April 2010, 04:39 PM   #37
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by sakis View Post
to be honest with you ...no i dont mind at all but i also dont understand what oposite means ...

...........

probably what you present is moded circuit of something else ...

kind regards sakis


( tinitus .... i can also sent you a proper pcb software for free if you want i have sprint layout 4 that i dont use any more since i have version 5 i will be more than happy to mail you a cd fo free ...probably it can make your pcb more undersatndable )
Thanks Sakis
I would like to try a software
Not that I need it much
But if I cant use it I could always pass it on to another member
Have tried another software suggested to me, and I couldnt make it work
So it may be wasted on me

Frontend and driver layout I have shown is 100% straight Dx, no changes so far...unless I have made mistakes
Mainly I do it to learn, and to put me in a position where I can at least hardwire output stage
A year ago I would have had no idea about it

I can see my post was confusing, with regards to saying that P3a and Dx maybe needing pushed in opposite direction to each other
1. I understand from Carlos as if Dx may be a bit on the soft side, which I interprit it as maybe being a bit grainy
2. I dont know P3a, but it sounds like you are saying you have pushed it in the direction of sounding softer, nicer

All in all, that indicates to me like P3a and Dx start out at opposite ends, regarding their sound nature
But I know all to well to NOT say stuff like that, considering having not heard any of them
But then, isnt that what describing sound is supposed to be good fore



So, how is the sound nature of P3a, before you modded it ?
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Old 29th April 2010, 06:05 PM   #38
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So, how is the sound nature of P3a, before you modded it ?

through the 3 years i ve been working arround from time to time with this amplifier starting with the first one that has been produced since day one it was made to rock from scratch in the pcb every litle detail was taken care of , and the material used was the best available nothing exotic this version was simply close to perfect

for fun i constructed some version with wrong pcb and low quality material that actually played bellow average

from all this time only a few days ago i ve seen that the 829-830 drivers made a serious audible diference as described above ...

beyond that i have never heard how this is working with Rods pcb and construction rules

for reference i will say once more that the construction i made is based on P3A schematic but features a couple of things like
matched ltp pair with thermal junction
silver mica, filter and miller,
multileyer driver miller cap ,
vbe attached to one of the driver
4 x 0.68 ohm output resistor ( results 10W 0.33 ) per tranistor
no inductor
2X10.000 mfd on board
and always except once 2sa1302 3281 original toshibas for the out

fairchild 1943+5200 sounded more muffy

so true comparsion with the original make of the P3A was never done ( hell it might as well play better than mine )

other than the above the P3A i make sounds as described in the first post

thanks for your time and interest

kind regards sakis
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Last edited by east electronics; 29th April 2010 at 06:07 PM.
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Old 30th April 2010, 12:48 PM   #39
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Default service akai am75

SERVICE AKAI AM 75

AKAI AM 75 visited my shop for repair seriously canibalized from a costumer that wanted to practice his repair skills ( very explosive !!! )

quiet a hard job to do since this amplifier features

1 gozillion curent surces
1 gozillion diferent rail voltage per division
modular style of construction
1 gozillion of wiring for almost everything ....

I wonder what the designer had in mind ???? never seen a so complicated machine with almost no reason ... ( for only 100+ watts at class AB and 65 ma of bias )

In a few words there is one board the is short of first stage and phono EQ and ofset controls
then there is another one that is called voltage amplifier and has every possible technology or any available techonlogy at the time and uses transitors fets current mirrors and current sources ( with also all the set up for line inputs on it )
then there is piggy board for the bias
now on the "mother board" is the main power supply ...Vi limmiters ... and another triple secondary power supply fully curent mirrored and stabilized with nine ( 9!!!! ) output transistors to regulate various voltages needed here and there ...

interwiring all these boards is a complete mess since to be able to fit all that in a 3U box was a pain in the @ss resulting all types of cables mixed and tied up all around

add to all the above that amplifier needs tone controls muting circuits and selector board all together with a digital input board ( !!! ) and your spaggheti is ready

never seen a japanese machine constructed in such a mess ( probably the designer was European ha ha ha ha )

got it repaired with all shorts of problems ( secondary psu, drivers and outputs blown to mars due to thermal stress and terible soldering)
and didnt even bother to listen to it

any body has a couple of years to spent to study the schematic ( that actually has a few mistakes ) i will be more than happy to provide

sorry i dindnt like it ... no photos no listenig comments
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Last edited by east electronics; 30th April 2010 at 01:00 PM.
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Old 6th May 2010, 07:16 PM   #40
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Default service AKAI AA 1050

A terrible machine ....compaired to todays standarts its a complete cr@@p

no serious damages a classic story ...all capacitors dead and replaced all pots and switches cleaned very carefully ( any day i will uprise a thread about contact cleaning with a new product i invented that seems to rock but still in testing mode ) ...a few lamps also replaced tuned...biassed ...idled it and go

enough power above 50 clean watts wonderful semis inside terrible crosstalk figures even though the selector switch is a mastepiece of engineering at the times signal rooting was terrible so everything jumps from here to there .... an average tuner with good sensitivity but not that good sound ...

Question why ???

why people spent money on machins like that ??? only a few things one that its nice to keep alive ...a unit like that will never be produced again in the feature... and then if you skip quality mambo jambo for a minute the sound that comes from this machine has unbeatable colorations that of course are not real or correct but very dear to listen ...

let us not forget that this machine has a very good chance to outperform me since its expeted to live another 30 years ...at least ..

regards sakis
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